package PTA.javabianchengjichu2;

import java.util.Scanner;

public class ex33 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a=sc.nextInt();
        int b = sc.nextInt();
        int c = sc.nextInt();
        int d = sc.nextInt();
        System.out.println(Math.abs(a-c)+Math.abs(b-d));



    }
}
